First of all let me explain what a structured walk is - it's an effective way of creating a strong bond between the human and the dog. Also, the human has the possibility to impose himself as leader if following the correct rules.
The structured walk allows the dog to satisfy his physical needs of exercise but also his psychological needs of exploration close to the leader - which means you.
Such a walk must take 10-20 minutes for pups, 30 minutes for small and medium sized adult dogs and up to 45 minutes for large dogs. This is necessary even if the dog has a yard to play.
The walk must be led by the human who always walks in front not allowing the dog to stray. The dog must focus on the human and on the walk and not on distractions around. Specialists recommend minimum 2 such walks/day.
I have heard of situations where dogs were kept inside the appartment for an entire week and their masters were wondering why they behaved in a chaotic manner. I have two neighbours who do this to their dog and he acts each time they take him out like he has just escaped from prison - running all over the place, biting other dogs, playing in a rough manner, barking for no reason.
To sum up, please walk your dog daily if you want to have him/her happy.